Question

A membrane has pure water on one side and a protein solution on the other. The membrane has pores equivalent in size to a spherical molecule with a molecular weight of 100,000. The protein solution consists of albumin (40g/L, MW=69,000),globulins (70 g/L, MW=150,000) and fibrinogen (60 g/L, MW=340,000). a) Assuming that the proteins form an ideal solution, what is osmotic pressure of the protein solution? b) What would be the osmotic pressure of the protein solution if the membrane was completely impermeable to proteins?

Answer 1

Concentration of protein solution = moles / volume

n = no of moles , v = vol of solution = 1 lit

no of mole of albumin = 40/69000 = 0.00057971 mol

no of mole of globulins = 70/150000 = 0.000466667 mol

no of mole of fibrinogen = 60/340000 = 0.000176471

total no of moles = 0.00122 mol

concentration = 0.00122/1 = 0.00122 M

Osmoticpressure = CRT = 0.00122 x 0.0821 x 298.15

                            = 0.02986 atm